A voting bloc is a group of voters that are so motivated by a specific concern or group of concerns that it helps determine how they vote in elections. The divisions between voting blocs are known as cleavage. A voting bloc can be longstanding and institutionalized, such as support for business or labor, or it can be created from scratch as the result of the saliency of a new public issue, such as a war or the potential resumption of a military draft. Ethnic groups are sometimes considered to be voting blocs, but it is unwise to simply assume that a majority of a given ethnic group will vote in one particular way, as economic status and religious beliefs also play an important role. Voting blocs grow and wane according to the development of issues and personalities. These blocs can often disappear and reappear with time and are not necessarily motivated by one single issue.
Voting blocs have been observed in the Eurovision Song Contest, with particular countries voting for their neighbors.
The term block voting is also used to refer to the concept of voting as a block, a system of winner take all decision-making whereby the vote of an entire electoral unit is cast in line with the majority decision of that unit, discounting any contrary votes. The most prominent example of this is in United States presidential elections, in which 48 of the 50 states cast all their Electoral College votes to the candidate winning a plurality. This leads to a "triage" strategy of presidential candidates aggressively trying to win narrow majorities in close swing states while avoiding campaigning in ones with a more certain outcome.
This system of block voting is also used in the UK by the Trades Union Congress; in an irony of history, it was introduced in 1895 by supporters of the Liberal Party to prevent or delay the establishment of the Labour Party, and it took the Labour Party from 1900 until 1993 to remove it from its own structures.
Combined with a local form of malapportionment, a system of mandatory voting blocks was also used within several states in the United States, especially Georgia in its county-unit system, to deny urban and minority populations equal representation until such systems were ruled unconstitutional in the 1960s with the Supreme Court case of Gray v. Sanders.
The single-party landslide result of these elections is very similar to the typical result in elections using the plurality-at-large voting system.